This invention relates to fasteners for attaching metal to wood, and more particularly to an improved railroad spike for attaching a metal rail to a wooden tie.
It is common in constructing tracks for trains to provide a rail or rails supported on cross ties formed of wood. The rails are commonly made of a metal such as steel, and are generally provided with mounting flanges. The mounting flanges are adapted to rest on metallic bearing plates, commonly referred to as tie plates or fishplates. The fishplates in turn rest on the wooden ties. It is common to employ spikes (i.e. cut spikes) for securing rails to ties. In the usual case, a spike is inserted in an opening or cavity in the fishplate and the spike shank is driven into the tie. The head of the spike is generally adapted to engage with the flange of the rail, thereby securing the rail to the tie. Alternatively, the fishplate may be equipped with a metal clip or boss that engages to the flange of the rail, and the head of the spike is adapted to engage with the fishplate to secure the rail to the tie.
After being in service for a short period of time, the ordinary spike often works loose from the tie due to the working action that occurs as the rail deflects under the load of passing trains and due to expansion and contraction of the wood fibers of the tie due to temperature, humidity and other environmental changes. Such loosening of the spike can necessitate replacement of the spike or other parts of the track assembly. Attempts to secure or anchor a spike by providing the shank with burrs, barbs, serrations or similar rough features adapted to engage with the wooden ties generally have proved unsatisfactory. Such spikes can be difficult to drive into a tie using manual or automated impact spike-driving methods. The rough feature may also chew or tear the wood fibers of the tie during installation, thereby causing damage to the tie.
In addition, after such spikes have been in service an appreciable length of time, they will have a tendency to work in the hole established in the tie by the spike shank. Working of the spike acts to enlarge the hole surrounding the shank and to damage the surrounding wood fibers, causing the spike to loosen over time. The enlarged hole may also permit water and other chemicals to enter the hole surrounding the spike shank, thereby further weakening the spike or the surrounding wood fibers. Removal of the spike usually causes additional damage to the tie; therefore, spike removal often requires replacement of the entire tie in order to ensure that the replacement spike will anchor the rail to the tie with sufficient holding power.
Spikes have been adapted with threaded shanks that can be screwed into the wooden tie. However, such spikes are difficult to install using manual or automated impact driving methods. Furthermore, such spikes generally require a pre-drilled hole in the tie to facilitate installation using rotary spike driving methods. Threaded spikes are also known to work loose under the load of passing trains. In an attempt to reduce working of spikes under load, attempts have been made to equip spikes with tabs or uniquely shaped shanks adapted to engage with the cavity of a fishplate, thereby locking the spike into engagement with the fishplate, reducing the tendency of the spike to work loose and damage the tie. Such spikes, however, are extremely difficult to install using automated impact spike-driving methods. In addition, such spikes can generally be used only in conjunction with a fishplate, and are extremely difficult to remove once locked into engagement with the fishplate.
The art continually searches for improved spikes suitable for use in securing a metal rail to a wooden tie. In particular, the art continues to search for spikes that exhibit a reduced tendency to work under the load of passing trains, for spikes that are readily removed and reinstalled without requiring replacement of the tie, and for spikes that are capable of installation using automated spike-driving methods.
This invention relates generally to an improved fastener for attaching metal to wood. More specifically, in one aspect, the invention features an improved railroad spike for attaching a metal rail to a wooden tie. The improved spike is well-suited for use with automated spike-driving methods, and is adapted to engage with the wooden tie to prevent or reduce loosening of the spike due to working of the spike under the load of a passing train, or due to expansion or contraction of the wood fibers in response to changing environmental conditions.
The improved spike is provided with a head having a flange, a metal stand-off extending axially from the flange, a plurality of flutes extending axially from the stand-off, and a threaded shank extending axially from the flutes to a tapered tip. The flutes are adapted to engage with wood to lock the spike into engagement with the tie, thereby preventing the spike from working loose due to mechanical loads imposed by passing trains or due to the influence of the elements.
In one embodiment, the head of the spike comprises a generally polygonal projecting tool grip extending axially from the flange on the side opposite to the threaded shank. The tool grip is adapted for engagement with a wrench to enable rotary driving of the spike into the tie or removal of the spike using a rotary motion imparted to the tool grip.
In a variation of this embodiment, the spike head is adapted for use with impact spike-driving methods. The head of the spike is preferably hemispherical or dome shaped and is adapted to for use with manual or automated impact spike-driving methods. Preferably, the hemispherical head is adapted to deform slightly under impact driving, thereby preventing damage to the tool grip.
In another embodiment, the threads are adapted to facilitate driving of the spike into the wooden tie using impact or rotary spike-driving methods, and to permit easy removal of the spike using rotary spike removal methods.
In a preferred variation of this embodiment, the threaded shank is adapted to permit driving of the spike into the tie using an impact driving method, and to permit easy removal of the spike using a wrench or other rotary spike removal method. The threads are adapted to cause rotation of the spike into the tie during installation using automated or manual impact spike-driving methods. The threads are preferably adapted to screw the spike threads into the wooden tie when a force is applied to the head of the spike in a direction generally towards the spike tip.
In a preferred embodiment, the improved spike is used with a metal tie plate or fishplate to secure the rail to the tie. In this embodiment, the length of the stand-off must be adapted to ensure that the flutes are at least partially engaged with the wooden tie when the spike is driven into the tie. The tie plate or fishplate preferably comprises a metal boss or an elastic fastener that is adapted to engage with the flange of the rail, thereby securing the rail to the tie when the spike is driven into the tie.
In another aspect, the invention features an improved railroad track assembly. The assembly comprises a metal rail, a wooden tie, a metal tie plate adapted to engage the rail, and an improved spike of the present invention. The improved spike is driven into the tie. The spike is adapted to fasten the tie plate and the rail to the tie. The improved spike comprises a head having an annular flange, a stand-off extending axially from the flange, a plurality of flutes extending axially from the stand-off, and a shank extending axially from the flutes to form a tapered tip. The flutes are adapted to engage the wooden tie. The stand-off has a length adapted to ensure that the flutes are at least partially embedded in the tie when the spike is used to fasten the tie plate and the rail to the tie.
In still another aspect, the invention features a method of using an improved railroad spike. An improved spike, a metal rail having a flange, a wooden tie and a metal fishplate having a cavity are provided. The improved spike is provided with a head having a flange, a metal stand-off extending axially from the flange, a plurality of flutes extending axially from the stand-off, and a threaded shank extending axially from the flutes to a tapered tip. The threads are adapted to facilitate driving of the spike into the wooden tie using impact or rotary spike-driving methods, and to permit easy removal of the spike using rotary spike removal methods.
In a preferred variation of this embodiment, an automated spike-driving method is used to drive the spike into the tie, thereby securing a metal rail to the wooden tie. Preferably, an automated impact spike-driving method is employed. In an alternative embodiment, a manual spike driving apparatus is used to drive the improved spike into the tie.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.